Process for handling fluids in heat transfer equipment

ABSTRACT

This invention provides a novel process of handling fluids which increase heat transfer efficiency in all types of heat transmission equipment. This process is applicable both to single and multiple units; in both cases, heat transfer is enhanced and steam consumption reduced. 
     Basically, the process consists in extracting, along with the condensate, some of the steam from inside of a steam heated unit, separating this steam from the condensate and noncondensable gases, before and after feeding this extraction steam to another units working at a lower pressure.

BACKGROUND OF THE INVENTION

In all of those industrial equipments and systems, utilizing steam as aheat transfer medium, there is a constant search for improved efficiencyin all parts, in order to reduce operating costs. To do it, piping isinsulated, leaks are eliminated, etc., nevertheless, there are alwayslosses which reduce efficiency and increase costs.

It is one of the objects of this invention to provide a procedure forhandling fluids in heat transfer equipment, that increases efficiencyand is applicable to individual or multiple units.

One additional object of the invention is to provide a process forextracting steam from a heat transfer unit, separating it from thecondensate and non-condensable gases, and reutilizing it in another unitat a lower pressure than the previous one.

Another important object of the invention is the extraction ofnon-condensable gases from inside of a unit. It is well known, among theskilled in the art, that it is necessary to extract certain amount of"live" steam in order to extract non-condensable gases. The processmakes use of devices to separate the non-condensables from theextraction steam, before and after utilizing this steam in other heattransfer units or as a humidifying medium.

The new process can be applied to any type of steam heated equipmentand, in this description, the novel process of this invention, will bedescribed as applied to a machine for paper and which consists ofseveral rotating cylinders, or dryers, heated with steam. However,reference is made to the paper machine installation, only as a practicalexample of the application of said procedure, but in no case to limitits field of application, which field is universal, as the process isapplicable to any industry or equipment that utilizes steam.

SUMMARY OF THE INVENTION

The novel process for handling fluids in heat transfer equipment, ofthis invention, basically consists in supplying steam to a unit or unitsby means of common pipes. Every unit has its own steam trap, modifiedwith a steam extraction device. The thus modified steam traps dischargethe condensate to a common pipe line which carries it into a "flashTank" described later on. Extraction steam is piped out from eachmodified steam trap into a common pipe header, which supplies thisextraction steam, through a separator, to another group of units.

The second group of units has also individual modified steam traps,except that, in this case, both the extraction steam and the condensateare piped together to the "flash tank."

The "Flash Tank" has the purpose of supplying steam to the lowestpressure units. Since the condensate that is discharged to the "FlashTank" is at a higher pressure, part of it flashes into steam when itenters the low pressure tank. This "Flash" steam, plus the extractionsteam from the second group of units, is supplied to the lowest pressureunits, thus resulting in the maximum utilization of the heat availablein the fluids supplied to the machine.

It should be noticed that all of the condensate is recovered and that nosteam is wasted to the atmosphere, as it is done in other conventionalprocesses.

DESCRIPTION OF THE DRAWINGS

In relation to the attached FIGURE, which depicts a paper dryingmachine, composed of multiple rotary cylinder dryers, heated with steam,it can be seen that there is a first group of cylinders 1, with a commonsteam supply header 2 and individual branch inlets 3. Each branch hasits own stop valve 4 at the inlet, and another stop valve 5, at theoutlet 6. Each outlet branch pipe 6 connects to a special separatingsteam trap 7. This special modified steam trap 7 receives condensate andsteam from the dryer cylinders 1, and it separates them, discharging thecondensate through pipe 8, with a stop valve 9, to header 10 and intoflash tank 11. The extracted steam is discharged through pipe 12, andstop valve 13 to header 14. This header 14 splits into two lines 14a and14b. Line 14a goes to a thermal non-condensable gas eliminator 15 whichdischarges the gases to atmosphere. Second line 14b goes into acondensate separator 16, from which a header 17 supplies the extractionsteam to a second group of cylinder dryers 18 by means of header 19 andstop valves 20. Condensate is drained from separator 16 by a normalsteam trap 22 through piping 21 to flash tank 11.

The second group of cylinder dryers discharges through individual branchpipes 23 and stop valves 24 to special separating steam traps 25 whichreceive both steam and condensate. In this case, the special traps 25discharge both condensate and extraction steam to a single pipe line 26which discharges to header 27, (common to the second group) and finallyto flash tank 11.

The flash steam produced at flash tank 11, is piped through line 28 to athird group through cylinder 29 (third in relation to the traveldirection of paper on the machine). This cylinder dryer 29 operates at alower pressure than the two groups described previously; from it, steamis extracted through pipe 30 to second cylinder dryer 31. From thissecond dryer 31 steam is also extracted through piping 32 to firstcylinder dryer 33. This manner of supplying steam to this group ofcylinders, produces an automatic pressure drop from one dryer to thenext. As a result of the pressure drop, each cylinder has a lowertemperature, in direction of the pressure drop, with the first cylinderin contact with the paper having the lowest temperature. The arrangementprovides a temperature gradient, rising in the direction of papertravel. Regulation of the pressure at flash tank 11 permits control ofthe temperature of the first dryer in order to avoid sticking of thepaper because of too high a temperature.

The discharge of each of these three dryers 29, 31 and 33 is throughbranch lines 34 and stops valves 35 to individual special separatingtraps 36 discharing both the condensates and the extraction steamthrough pipe 37 to final condensate collector tank 38 from where theyare pumped to the boiler.

The condensate from the flash tank 11 is also discharged, through anormal trap 39 to the condensate collector tank 38.

The invention has been described in accordance with its preferredcharacter, taking in consideration that it has been referred to a paperdrying machine as a practical application, but with the fullunderstanding that the procedure, subject on this invention, is in noway limited to the paper industry. Furthermore, it is understood thatany variation on installations, based on the present description, willnecessarily fall within the scope of the invention.

I claim:
 1. Process for handling fluids in heat transfer apparatus,comprising the steps of providing a first group of heat transfer units,feeding .Iadd.a flow of .Iaddend.steam to this first group, through acommon header; connecting the outlets of said heat transfer units tofirst modified steam-trap units .[.to traps.]. that separate condensateand extraction steam.Iadd., thereby providing a flow of condensateseparate from a flow of extraction .Iaddend.steam; piping the condensateflow through a common header to a flash tank and feeding the .Iadd.flowof .Iaddend.extraction steam to a second group of heat transfer units,through a separator and an air eliminator; .[.in this second group ofheat transfer units, the steam is passed through corresponding steamtraps, but in this case the steam traps.]. .Iadd.feeding the flow ofextraction steam to the second group of heat transfer units, through acommon header; connecting the outlets of the second group ofheat-transfer units to second steam modified traps, the second steamtraps being connected to .Iaddend.discharge, both the extraction steamand the condensate, together through a header to the flash tank;.Iadd.connecting .Iaddend.said flash tank .Iadd.to feed.Iaddend..[.feeds.]. the flash steam through a pipe to one of the heattransfer units of a third group, that operates at the lowest pressure ofall groups; .[.from this unit, steam is extracted to the next unit andfrom the latter to a third unit,.]. .Iadd.extracting steam from said oneunit and feeding the same to a second unit of the third group, andextracting steam from said second unit and feeding the same to a thirdunit of the third group, .Iaddend.producing by .[.this.]. .Iadd.such.Iaddend.extraction an automatic pressure drop from one unit to thenext.
 2. Procedure for handling fluids in heat transfer apparatus inaccordance with claim No. 1, characterized by providing a .[.group ofsteam traps.]. .Iadd.modified steam trap .Iaddend.for each of the unitsin the third group; these traps .Iadd.being connected to.Iaddend.discharge, both the condensate and the extraction steamtogether, through a pipe to a final condensate collector .[.that alsocollects the condensate that a normal trap discharges out of the flashtank.]..Iadd., and connecting a normal trap to receive condensatedischarged from the flash tank and to supply the same to said finalcondensate collector. .Iaddend. .[.3. Procedure for handling fluids inheat transfer apparatus, in accordance with claim No. 1, wherein theextraction steam is condensed in other groups of heat transfer units..]..[.4. Procedure for handling fluids in heat transfer equipment, inaccordance with claim No. 1, wherein individual drainage is provided foreach heat transfer unit, collecting the condensates in general headersthat discharge into collector tanks..]. .[.5. Process for multi-stagehandling of fluids in plural heat-transfer stages comprising the stepsof feeding steam to heat-transfer apparatus of a first of said stages;extracting an outlet flow from said first-stage apparatus, separatingsaid flow into a line of first-stage vapor flow apart from a line offirst-stage condensate flow, and feeding said first-stage vapor flowdirectly to heat-transfer apparatus of a second of said stages;extracting an outlet flow from said second-stage apparatus, separatingsaid last-mentioned flow into a line of second-stage vapor flow apartfrom a line of second-stage condensate flow, and directly utilizing thesecond stage vapor flow in a third heat-transfer apparatus..]. .[.6. Theprocess of claim 5, wherein in the first stage, steam is fed to aplurality of first-stage heat-transfer units, and wherein thefirst-stage step of separating vapor flow from condensate flow isperformed individually for the respective outlet flows from theindividual heat-transfer units..]. .[.7. The process of claim 5, whereinin the second stage, steam supplied by the first-stage vapor-flow lineis fed to a plurality of second-stage heat-transfer units, and whereinthe second-stage step of separating vapor flow from condensate flow isperformed individually for the respective outlet flows from theindividual heat-transfer units..].
 8. The process of claim .[.6.]..Iadd.12.Iaddend., wherein the .[.condensate flows separated from theoutlet flows of individual heat-transfer units are fed.]..Iadd.last-defined step comprises feeding the separated second-stageoutlet condensate and vapor flows .Iaddend.to a flash tank .[.thelatter.]. .Iadd.to generate flash steam, and .Iaddend.feeding flashsteam to .Iadd.the .Iaddend.third-stage heat-transfer apparatus.
 9. Theprocess of claim 8, wherein .Iadd.both the first-stage and .Iaddend.thesecond-stage condensate .[.flow is also.]. .Iadd.flows are .Iaddend.fedto the flash tank for generation of flash steam supplied to thethird-stage heat-transfer apparatus. .[.10. The process of claim 5, andthe step of blocking said first-stage condensate flow for less than afirst-stage minimum predetermined pressure differential between thepressure of the first-stage outlet flow and the pressure in thefirst-stage condensate line..]. .[.11. The process of claim 5, and thestep of blocking said second-stage condensate flow for less than asecond-stage minimum predetermined pressure differential between thepressure of the second-stage outlet flow and the pressure in thesecond-stage condensate line..]. .Iadd.
 12. Process for multi-stagehandling of fluids in plural heat-transfer stages, each of which stagescomprises a plurality of heat-transfer devices, comprising the steps offeeding steam in parallel to each of a plurality of heat-transferdevices of a first of said stages; extracting a continuous outlet flowfrom each of said first-stage devices, separating each said flow into aline of first-stage continuous vapor flow apart from a line offirst-stage condensate flow, collecting into a common first-stage vaporline the individual separated continuous vapor flows from each of saidfirst-stage devices, collecting into a common first-stage condensateline the individual separated condensate flow from each of saidfirst-stage devices, said common first-stage condensate line beingindependent of said common first-stage vapor line, and directly andcontinuously utilizing the continuous vapor flow in the commonfirst-stage vapor line in a second-stage heat-transfer device. .Iaddend..Iadd.
 13. The process according to claim 12, in which vapor flow in thecommon first-stage vapor line is directly utilized by parallel feedingof such vapor flow to a plurality of second-stage heat-transfer devices..Iaddend. .Iadd.
 14. The process of claim 13, and the steps ofextracting an outlet flow from each of said second-stage devices,separating each said last-mentioned flow into a line of second-stagecondensate flow apart from a line of second-stage vapor flow, andutilizing separated second-stage outlet flows in a third stage ofheat-transfer apparatus. .Iaddend. .Iadd.
 15. Multi-stage steam-operatedapparatus, comprising a first stage of plural heat-transfer deviceshaving parallel steam-supply inlet connections, an independentoutlet-flow connection for each of said first-stage devices, meansincluding a modified steam trap in each of said outlet-flow connectionsfor separating each outlet flow into an individual first-stagecontinuous vapor flow apart from an individual first-stage condensateflow, a vapor-flow header connected to receive each said individualfirst-stage vapor flow, a condensate header independent of saidvapor-flow header and connected to receive each individual first-stagecondensate flow, and a second stage of plural heat-transfer deviceshaving steam-supply inlet connections connected for supply by saidvapor-flow header. .Iaddend..Iadd.
 16. Apparatus according to claim 15,in which each said second-stage heat-transfer device includes anindependent outlet-flow connection, a second-stage outlet-flow header,individual modified steam traps connecting said second-stage header tosaid second-stage outlet-flow connections, and flash-steam generatingmeans having a condensate-supply connection to said condensate headerand having a vapor-supply connection to said second-stage header..Iaddend..Iadd.
 17. Apparatus according to claim 15, in which theconnection of said vapor-flow header to the inlets of said second-stageheat-transfer devices includes a separator for separating condensatefrom vapor flow, the vapor flow being connected to the inlets of saidsecond-stage heat-transfer devices, a flash tank, and means including asteam trap connecting the last-separated condensate for supply to saidflash tank. .Iaddend. .Iadd.
 18. Apparatus according to claim 15, inwhich the connection of said vapor-flow header to the inlets of saidsecond-stage heat-transfer devices includes an air eliminator forextracting non-condensable gas from the vapor supply to saidsecond-stage devices. .Iaddend..Iadd.
 19. Apparatus according to claim15, in which said second-stage devices are serially connected for supplyby said vapor-flow header, and condensate-trap means at each seriesinterconnection. .Iaddend.